After several days of active weather across the High Plains, it looks as if things could be shifting east toward the Midwest, if only for a day. Sunday, during the afternoon and evening in particular, looks to be fairly noisy across portions of Illinois, Indiana, and Ohio. The Storm Prediction Center has placed central Illinois and Indiana under an 'Enhanced Risk' for severe thunderstorms on their Day 2 Outlook, highlighting Sunday, June 7th.
It does appear that a full spectrum of severe weather threats will be possible across central Illinois, Champaign-Urbana included. This will include the potential for primarily damaging winds, but in addition large hail, flooding rains, and perhaps even isolated tornadoes.
How will things unfold? There are several different solutions being offered up by various computer forecast models right now, but I am buying into one particular scenario. We'll see numerous thunderstorms developing over Nebraska and Iowa this evening as they deal with their own severe weather threat. These storms will likely organize into an eastward moving cluster and push across Iowa into northern Illinois during the overnight and early morning hours. The severe weather threat with these storms once they reach northern Illinois late tonight will be low, but their role in tomorrow's weather is crucial.
As they decay and move off into Indiana during the early morning hours, these storms will leave an 'outflow boundary' in their wake. A boundary separating the rain cooled air where the storms have passed, and the hot and humid air to the south where storms did not occur. This boundary separating the hot & humid vs. rain cooled air will be the focal point for thunderstorms to erupt during the hours of peak heating on Sunday afternoon.
The atmosphere across central Illinois will be very unstable, with temperatures reaching toward 90 degrees, and dew points pushing into the 70 degree range. This instability will provide plenty of energy for thunderstorms to develop and perhaps quickly reach severe levels. Adequate wind shear will be in place for sustained supercells, and is borderline adequate for a couple tornadoes to occur in central Illinois as well. The tornado threat appears slightly conditional in our area... I won't get into specifics, but in addition to adequate wind shear being in place, there is a lot to be said for way, or orientation that these storms develop. Tornadoes are finicky, and things need to be *just right* for their development, and the orientation of the boundary that these storms will be forming on leads me to believe that Sunday could end up more of a damaging wind/flooding rain type event from eastern Illinois into Indiana.
That being said - don't take it lightly. The instability is certainly there, and the wind shear isn't completely absent either, so while it may not appear to be a large scale tornado day, one or two tornadoes certainly aren't out of the realm of possibility in central/eastern Illinois on Sunday afternoon/evening and you don't want to be the one that ends up unpreprared with one in your backyard.
Here are a few graphics for those more visually inclined: